1. Field of the Invention
The present invention relates to a shape controlling method for rolled sheet material.
The method of controlling the shape of a rolled sheet material necessitates the detection of the shape of the rolled sheet material by a shape detector and the recognition of the pattern of the detected shape. The shape of the rolled sheet can be expressed in terms of distribution of factors such as the steepness, defined more fully hereinbelow, elongation, stress or sheet thickness in the breadthwise direction of the sheet. Shape control is conducted by operating final control elements in such a manner that the detected shape coincides with a desired shape.
2. Description of the Prior Art
In order to attain the desired shape of a rolled sheet material, the actual shape is detected by a shape detector and a pattern of the detected shape is determined. Attempts have been made to express the shape pattern in terms of a series to the fourth power. Actually, however, the pattern does not always change smoothly or gently over the breadth of the rolled sheet material, and it has often been experienced that the pattern abruptly changes in regions near the with or breadthwide ends of the sheet material. It is, therefore, advisable to use a higher power series degree, e.g., sixth power, for expressing the shape pattern.
As stated before, the shape control is conducted by operating a plurality of final control elements in such a manner that detected shape pattern coincides with the desired shape pattern. This, however, encounters the following problems.
First, considerable time is required for the determination of the operating variables, because of interference between the final control elements. It follows that the shape control for attaining the desired shape is extremely difficult.
Secondly, it is to be pointed out that the control of the operating variable of one final control element with direct regard to the operating variables of other elements of the distribution of those which have to be done when the one final control element has achieved its control variable, are extremely difficult to carry out, so that further enhancement of the shape toward the desired shape is not achieveable.
Thus, there are practical limits in to the shape control effected by the conventional shape controlling methods, and therefore it is necessary to develop an improved shape controlling method.
In U.S. Pat. No. 4,320,643, a technique for asymmetric shape correction is proposed however, there is no indication as to the manner in which signals are delivered from the shape detector to the final control elements nor any suggestion as to a control for avoiding interference between different final control elements.
An article entitled "Analysis of Shape and Discussion of Problems of Scheduling Set-up and Shape Control", P. D. Spooner, G. F. Bryant, Publ. Met. Soc 1976, mentions shape parameters formed by signals derived from the shape detector, as well as the effect of differences between the roll-reduced position in on the shape of the rolled sheet material, but does not show at all which control element is controlled by each of the signals derived from the shape detector.